This research project is now in its fourth year. Its main purpose is to investigate the effect of exercise training on genetic animal models of hypertension. Our results to date indicate that early exercise training will delay and blunt the rise in blood pressure that occurs with muturation. However, it can not normalize pressure in SHR populations without supplementation of anti-hypertensive drugs. To explain these and related changes, we have postulated that alterations are occurring in baroreceptor sensitivity, wall-lumen relationships, sympathetic nerve activity, vascular activity, and venous compliance. To test these postulates, training studies with sympathectomized animals will be conducted with SHR populations; unanesthetized rats will be subjected to LBNP test conditions; aortic, iliac femoral and caudal arteries will be perfused for measurement of wall and lumen areas and ratios; both aortic strips and hind limb perfusion (Brody) data will be used to evaluate vascular reactivity of arteries to various vasoconstrictor and vasodilator compounds. In addition attempts will be made to measure compliance in isolated strips and bloodflow in selected arteries while exercising. Emerging from these investigations should be additional data on the general effect of training on animal models, some new insights on the response of SHR to training; and new data on the response of trained unanesthetized rats to LBNP.